Run `delete-notifications-older-than-retention` at 3am
Run `delete-notifications-older-than-retention` at 3am

Moving it from 4:15am to 3:00. This will mean we do more deleting before
the 'work day' starts and improve our DB performance.

I've looked at the last 14 day of logs for the
`create-nightly-notification-status` subtasks and the
`create-nightly-billing` subtasks. The latest they appear to finish is
2.30AM. There were some outliers but I believe these were people running
the tasks in the middle of the day as a manual process.

Obviously, this still means there is a risk that those tasks conflict
with `delete-notifications-older-than-retention`, even more so now that
we move this to 3am.

alphagov/notifications-api,alphagov/notifications-api